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Dr Tim Fox Head of Energy and Environment

Institution of Mechanical Engineers

Cryogenics for Storing Air

for Electricity Generation in a UK Policy Context

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Fully engaged in public debate

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Introduction

Overview

Policy landscape and drivers

Energy storage

A novel cryogenic approach

Pilot plant project

Barriers

Policy needs

Conclusions

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UK energy landscape

• Stable demand profile for past three decades

• Need to replace ageing plant and infrastructure

• North Sea gas depleting (by 2020, 80% of gas demand will need to be met through imports)

• Increasing global competition for limited primary energy resources, particularly oil and gas

• Decarbonisation aspirations and obligations (targets)

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UK Energy policy

Sustainability • EU 20 / 20 /20

targets • Climate Change

Act 2008 • Increased

renewables • Decarbonisation of

electricity • Decarbonisation of

other sectors • Increased use of

electricity as a clean energy vector

• Energy conservation • Energy efficiency • Distributed

generation

Security of supply • Licence conditions

provide requirements for supply

• Ensure sufficient peak capacity (Winter)

• Maintain margin with adequate reserves

• Increase renewables and nuclear to reduce reliance on imported gas and other fuels

• Develop system flexibility and community level resilience

• Adopt smart grids • Invest in storage

Economy • Open markets

deliver competitive prices

• Interconnections link markets

• Avoid price uncertainty for consumers

• Political intervention and regulation to protect consumers

• Community and domestic stakeholder participation in ownership, production and trading

• Asset optimisation

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Generation under ‘Gone Green’ scenario Source: National Grid

Future generation mix

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Year

Ge

nera

tio

n C

ap

ac

ity (

GW

)

OCGT

Oil

Pumped Storage

Interconnectors

Wind

Gas (CCGT+CHP+MGT )

Coal

Hydro

Wave and Tidal

Biomass

Nuclear

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Renewables and power system

Large scale and small scale

Variability and location

Surplus and shortfall

Short and long term reserves

Markets/subsidies

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UK power network

• Large scale competitive generation, regulated transmission and distribution

• Limited embedded generation (at distribution level)

• Wholesale market supplies retail customers

• Limited number of self suppliers

• System planned to meet peak demand plus reserves – spare (or under utilised assets)

• Low level of interconnections to other networks

• Regulated wires businesses • Facing substantial change

• Significant shift from dispatchable generation to time variable generation

• Peaky demands from digital society, switch to heat pumps, uncertain effect of electric vehicles

• Distributed community and domestic level generation and trading

• Average and peak domestic demand likely to increase

• Balancing the system requires more flexibility

• Higher level on continental interconnection

Today’s network The future

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Tools for system balancing

Flexible

generation

(reserve)

Storage (absorbs and

rejects power)

Connectors

(import or

export)

Demand

response

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Storage – enabling technology

• Flexibility of scale and location

• Intermittent renewable energy sources

Mix of storage technologies analogous to generation mix

Defers network investments and lowers system costs

Reduces SMART grid and interconnection risks

• Large base-load electricity generation

‘Wrong time’ electricity generation – too much or too little

Optimises return on investment (ROI) in renewables plant

Reduces need for idle spare capacity (reduces investment costs in asset base) and avoids (volatile) fuel costs

Sweats assets for improved ROI – e.g nuclear and biomass

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Enablers – electricity storage

• Pumped hydro

• Compressed-air

• Power to gas

• Flywheels

• Thermo processes

• Batteries and capacitors

• Fuels

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Application scales and potential users

Storage application matrix

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Using cryogenic technology

• Principles Use liquefied air or liquid nitrogen as storage medium

Mature technology from air separation industry

Proven ‘standard’ equipment in daily use with well established supply chains

Energy density of cryogen compares well with other medium

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Highview Power Storage Ltd

• The Company

• Pilot Plant

Established 2005 to design and develop utility-scale energy storage and power systems

$18m equity investment plus $1.8m DECC capital grant

UK company based London with pilot plant in Slough

Working with UK Universities to develop technology further

300kW hosted by SSE at Slough Heat & Power

Operating since April 2010, fully integrated into local distribution network

Tim Fox thanks the Directors of Highview Power for permission to present this work and the engineering staff for assistance in preparing this talk.

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The storage cycle

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The plant (1)

300 kW turbine output, 20° (68°) to 60°C (140°F) inlet temp

30 tonne/day liquefier, 2.5 MWhrs storage

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The plant (2)

• Milestones

2005 – research begins University of Leeds

2008 – pilot plant project starts November

Power recovery and cold recovery ops Spring 2010

2010 – STOR service trials begins

Cold storage, recycle and liquefaction ops Spring 2011

2011 - Triad service trials

2012 – pilot successful – next step commercialisation

Note: STOR = Short Term Operating Reserve – balancing duty

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Value of cold recycle

Available enthalpy for cold cycle ~300kJ/kg of liquid product

Cycle simulation indicates near term target thermal storage efficiency of 80% would deliver >50% cycle efficiency

Achieved on pilot plant

Target cold recycle at full scale

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TS diagram for power recovery

Four Stage Expansion

With re-heat between

stages

Compression of cryogenic liquid

Heat addition at

Constant pressure

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The value of waste heat

More work recovered

with use of waste heat

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Commercial service trials

Summary of STOR trials

Over 2 week period achieved 94.6% availability.

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Results - Power recovery

Time (minutes)

Power (kW)

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Pilot outcome

• Overall

Highview have successfully demonstrated use of cryogenic technology for electricity storage at pilot plant scale

Viability of cold recycle to improve efficiency of cryogen manufacture

Use of waste heat for cycle efficiency improvements

Ability to deliver commercial reserve services

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Possible next steps

• Commercial scale demonstration

10 MW output with >50% efficiency

Liquefier sized to suit market application

100’s MWs output with GWhs storage

Capital cost ~$900 to $1900/kW

Annual O&M cost ~2% capital cost

No geographical constraint and benign environmentally

70% efficient with waste heat at 239°F

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Barriers and challenges

• Research, development and demonstration funding

• Classification of storage solutions

• Electricity market structure

Electricity “consumer” and electricity “generator”

Competitive generation market and highly regulated transmission and distribution provider

Need to be allowed to access multiple income streams

Lack of incentivisation

DECC Energy Storage Technology Demonstration

£0.5 million for 12 organisations – feasibility of ideas

DECC Storage Component Research & Feasibility Study

£1.5 million for 4 companies to improve materials and explore systems in UK electricity networks

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Policy needs

• Separate classification for storage

• Recognise the value of storage

• Create competitive incentivised environment

• Support demonstration at commercial scale

Strongly dependent on network generating mix and local market rules

Recognise unique roll as both ‘consumer’ and ‘provider’

Needs to ensure inclusion and access to multiple streams

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Conclusions

• Develop policy frameworks and mechanisms that reward value of electricity storage in UK power markets

• Create a shop-window for UK electricity storage technology so innovations can be seen and sold

• Encourage/support UK companies and research organisations that are developing and demonstrating storage technologies

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Thank you

@TimFox_IMechE

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Storage comparisons